1. Field of the Invention
The present invention relates to a connecting structure for covered wires where their respective conductors are connected to each other by oscillating respective insulating covers of the wires with ultrasonic waves. More particularly, it relates to a connecting structure which is effective to connect a shield wire with a ground wire.
2. Description of the Related Art
Generally, it is complicated and troublesome to handle a shield wire having a braided wire coaxially disposed around a core line (or core lines) with the deteriorated workability in using the shield wire. As an effective measure for improving the deteriorated workability, there is provided a connecting structure for wires which takes advantage of inside heating due to the ultrasonic oscillation in Japanese Unexamined Patent Publication (kokai) No. 7-320842.
In the publication, there are shown two kinds of covered wires. One is a shield wire which comprises a core line, an inside insulating rind arranged outside the core line, a braided wire as a shield conductor arranged outside the inside insulating rind, and an outside insulating rind. The other is a ground wire consisting of a core line and an outside resinous rind arranged outside the core line.
According to the disclosed method of connecting the braided wire of the shield wire connected to a connector, to the core line of the ground wire also connected to the connector, in front of the connector, the ground wire is first overlaid on the shield wire so that they cross each other at a connection point. Next, the overlapping portions are interposed between upper and lower resin tips. Then, while compressing the upper and lower resin tips from the outside, they are subjected to ultrasonic oscillation by making use of an ultrasonic horn and an anvil. Consequently, both of the outside rinds of the shield wire and the ground wire are molten for elimination, so that the braided wire of the shield wire comes into electrical contact with the core line of the ground wire. Simultaneously, the upper and lower resin tips are mutually welded to each other in order to seal the vicinity of the above connecting point. Note, in the modification, there is a case that the upper and lower resin tips are respectively provided, on bearing faces thereof, with wire-accommodating shallow grooves for positioning the shield wire.
However, the so-obtained connecting structure has a problem in that if the positions of the upper and lower resin tips deviated from each other during the ultrasonic oscillation for welding, the welding strength between the upper and lower resin tips deteriorated due to the reduced welding area. In addition, such a positional deviation between the upper and lower resin tips would cause the connecting condition between the braided wire of the shield wire and the core line of the ground wire to be varied widely, so that the stability in electrical performance would deteriorated, too.
Under such a circumstance, it is therefore an object of the present invention to provide a connecting structure for covered wires, which is capable of preventing the mutual deviation in position between the upper resin tip and the lower resin tip at the ultrasonic oscillation, whereby the welding strength and the stability in electrical performance can be ensured.
The object of the present invention described above can be accomplished by a connecting structure for covered wires, comprising:
a first covered wire having a first conductor covered with a first resinous cover;
a second covered wire having a second conductor covered with a second resinous cover, the second conductor being electrically connected with the first conductor of the first covered wire cross each other; and
an upper resin tip and a lower resin tip between which an electrical connecting part of the first and second conductors and the surroundings are interposed, the upper resin tip being welded to the lower resin tip while interposing the first and second covered wires between the upper resin tip and the lower resin tip;
wherein either one of the upper and lower resin tips is provided, on a periphery of a butt face thereof to be abutted against the other resin tip, with a projecting rim, while the other of the upper and lower resin tips is provided, on a periphery of a butt face thereof being abutted against the other resin tip, with a recessed rim for engagement with the projecting rim;
whereby the upper and lower resin tips can be located and integrated by the engagement of the projecting rim with the recessed rim.
With the above-mentioned connecting structure, owing to the engagement of the projecting rim with the recessed rim, it is possible to exclude a possibility that the upper resin tip deviates from the lower resin tip during the ultrasonic oscillation. Therefore, it is possible to ensure a constant welding area, whereby the reliability in connecting strength can be improved. In addition, since there is no deviation in contact between the first conductor and the second conductor, the electrical connecting performance can be stabilized.
In the present invention, preferably, the first covered wire is a shield wire, while the second wire is a ground wire and wherein the first conductor is a shield conductor of the shield wire, while the second conductor is a core line of the ground wire.
With the above-mentioned connecting structure, since the upper resin tip does not deviate from the lower resin tip during the ultrasonic oscillation, it is possible to exclude a possibility of deviating a contact between the braided wire and the core line, whereby the electrical connecting performance can be stabilized, too.
In the connecting structure of the invention, preferably, the second covered wire is withdrawn to the exterior of the upper and lower resin tips, across the projecting rim and the recessed rim in engagement with the projecting rim.
In this case, with such a withdrawal of the second covered wire, the second conductor is bent irregularly in the welded structure, so that the drawing resistance of the second covered wire can be enhanced.
In the present invention, preferably, each of the upper and lower resin tips is provided, on its butt face being abutted against the other resin tip, with a wire receiving groove which has a semi-circular cross section having a diameter substantially equal to a diameter of the first covered wire.
According to the preferred connecting structure, since the diameter of the wire receiving groove is substantially equal to the diameter of the first covered wire, it is possible to weld the upper resin tip to the lower resin tip in the wrapping manner without compressing the first resinous cover of the first covered wire. Thus, since there is no possibility that the first resinous cover of the first covered wire is torn or broken by the upper or lower resin tip, the fixing force between the upper and lower resin tips and the first covered wire can be enhanced. In addition, it is possible to exclude a possibility that the first covered wire exposes the first conductor in the vicinity of the upper and lower resin tips.
According to the invention, there is also provided a method of producing a connecting structure for covered wires, the method comprising the steps of:
preparing a first covered wire having a first conductor covered with a first resinous cover and a second covered wire having a second conductor covered with a second resinous cover;
overlaying the second covered wire on the first covered wire cross each other;
interposing respective overlapping portions of the first and second covered wires between an upper resin tip and a lower resin tip; and
oscillating the upper and lower resin tips with ultrasonic waves while compressing the upper and lower resin tips from the outside, whereby the first and second resinous covers of the first and second covered wires are molten for removal thereby to bring the first conductor of the first covered wire into electrical contact with the second conductor of the second covered and simultaneously, the upper and lower resin tips are mutually welded to each other thereby to seal up the surroundings of a contact between the first conductor and the second conductor;
wherein either one of the upper and lower resin tips is provided, on a periphery of a butt face thereof to be abutted against the other resin tip, with a projecting rim, while the other of the upper and lower resin tips is provided, on a periphery of a butt face thereof to be abutted against the other resin tip, with a recessed rim for engagement with the projecting rim;
whereby the upper and lower resin tips can be located and integrated by the engagement of the projecting rim with the recessed rim.
In the above-mentioned method, preferably, the first covered wire is a shield wire, while the second wire is a ground wire and wherein the first conductor is a shield conductor of the shield wire, while the second conductor is a core line of the ground wire.
In the above-mentioned method, preferably, the second covered wire is withdrawn to the exterior of the upper and lower resin tips, across the projecting rim and the recessed rim in engagement with the projecting rim.
In the above-mentioned method, preferably, each of the upper and lower resin tips is provided, on its butt face being abutted against the other resin tip, with a wire receiving groove which has a semi-circular cross section having a diameter substantially equal to a diameter of the first covered wire.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawings.